When a light ray moves from denser to rarer medium, which of the following conditions results in total internal reflection?

The correct answer is Angle of incidence (i) > critical angle (ic).

Key Points

• Total internal reflection occurs when the light ray travels from a denser medium to a rarer medium.
• The phenomenon happens when the angle of incidence (i) exceeds the critical angle (ic) for the two media involved.
• The critical angle is the angle of incidence in the denser medium at which the refracted ray in the rarer medium travels parallel to the surface.
• If the angle of incidence is greater than the critical angle, the ray is completely reflected back into the denser medium instead of being refracted.
• This principle is widely used in optical technologies such as fiber optics, binoculars, and total internal reflection prisms.

Additional Information

• Critical Angle:
  • The critical angle is defined as the angle of incidence in a denser medium for which the angle of refraction in the rarer medium is 90°.
  • It depends on the refractive indices of the two media involved.
  • The formula to calculate the critical angle is sin(ic) = n₂ / n₁, where n₁ and n₂ are refractive indices of the denser and rarer medium respectively.
• Refractive Index:
  • The refractive index is a measure of how much the speed of light is reduced in a medium compared to vacuum.
  • A higher refractive index indicates a denser optical medium.
• Applications of Total Internal Reflection:
  • Used in optical fibers for efficient transmission of light signals over long distances.
  • In diamond cutting, the sparkling effect is due to total internal reflection.
  • Utilized in periscopes and binoculars for better image quality.
• Conditions for Total Internal Reflection:
  • Light must travel from a denser medium to a rarer medium.
  • The angle of incidence must be greater than the critical angle.